At what age can asthma be diagnosed and what is the role of syrup salbutamol (albuterol) in viral wheeze?

Diagnosis of Asthma in Children and Role of Salbutamol in Viral Wheeze

Age-Specific Diagnosis of Asthma

Asthma diagnosis should be based on objective testing in children aged 5-16 years, while in children under 5 years, a clinical approach with therapeutic trials may be necessary due to limitations in diagnostic testing. 1

Children 5-16 Years

• Diagnostic approach requires objective testing:

  • Spirometry with bronchodilator reversibility (BDR) testing is the first-line test
  • Abnormal results: FEV1 or FEV1/FVC <80% or below lower limit of normal (LLN)
  • FeNO testing (value ≥25 ppb supports diagnosis)
  • At least two abnormal objective test results are required for diagnosis 2

• Diagnostic algorithm:

  1. FeNO measurement (ideally before spirometry)
  2. Spirometry
  3. BDR testing (if spirometry abnormal)
  4. Challenge testing or PEFR variability if initial tests inconclusive 1

Children Under 5 Years

• Diagnosis is more challenging due to:

  • Inability to perform reliable spirometry
  • Difficulty distinguishing from viral-induced wheezing
  • Similar symptoms in other conditions 2, 3

• Clinical approach for diagnosis:

  • Recurrent wheeze is the most important symptom (sensitivity 0.55-0.86, specificity 0.64-0.90) 1
  • Consider risk factors for persistent asthma:
    • Parental history of asthma OR physician diagnosis of atopic dermatitis
    • Diagnosed allergic rhinitis, peripheral blood eosinophilia >4%, or wheezing apart from colds 2
  • Frequency of symptoms: >3 episodes of wheezing in past year lasting >1 day and affecting sleep 2

Role of Salbutamol in Viral Wheeze

Salbutamol (albuterol) syrup can be used for symptomatic relief in viral wheeze, but should not be used as a diagnostic tool alone and is not recommended for long-term management of viral wheeze. 4

Mechanism and Efficacy

• Salbutamol acts on beta-2 adrenergic receptors in bronchial smooth muscle, causing relaxation 4
• Most patients show improvement in pulmonary function within 5 minutes of administration 4
• Maximum average improvement occurs at approximately 1 hour and can last 3-6 hours 4

Guidelines for Use in Viral Wheeze

• Short-term symptomatic relief:

  • May provide temporary bronchodilation during viral respiratory infections
  • Not recommended as a diagnostic tool alone 2
  • Should not be used as the sole basis for asthma diagnosis 2

• Limitations:

  • Response to bronchodilators in viral wheeze may be variable and does not confirm asthma diagnosis
  • Regular use is not recommended for viral-induced wheeze without confirmed asthma 2

Safety Considerations

• Pediatric use is supported for children 2 years of age or older 4
• Safety and effectiveness in children below 2 years have not been established 4
• Cardiovascular effects can occur in some patients (increased pulse rate, blood pressure changes) 4

Distinguishing Asthma from Viral Wheeze

• Key differences:

  • Viral wheeze typically resolves between episodes
  • Asthma shows persistent symptoms or recurrent episodes triggered by multiple factors
  • Viral wheeze is more common in children under 5 and often resolves by school age 5

• Predictors of persistent asthma vs. transient viral wheeze:

  • Family history of asthma
  • Personal history of atopy (eczema, allergic rhinitis)
  • Wheezing without colds
  • Peripheral blood eosinophilia 2, 6

Common Pitfalls in Diagnosis

1. Over-reliance on symptoms alone:

   • Symptoms alone are insufficient for diagnosis (strong recommendation against) 2
   • Chronic cough as the only symptom is unlikely to be asthma 2

2. Inappropriate use of medication trials:

   • Trial of medication should not be used alone for diagnosis 2
   • Only consider medication trials in children with abnormal spirometry and negative BDR 2

3. Failure to consider alternative diagnoses:

   • Foreign body aspiration
   • Congenital airway abnormalities
   • Cystic fibrosis
   • Primary immunodeficiency
   • Vascular ring
   • Tracheomalacia 2, 1

4. Assuming all wheeze is asthma:

   • Approximately 40% of children wheeze in their first year of life
   • Only 30% of preschoolers with recurrent wheezing still have asthma at age 6 6

By following these guidelines, clinicians can more accurately diagnose asthma in children of different age groups and appropriately use salbutamol in the management of viral wheeze.